U.S. Pat. Nos. 4,455,768 and 4,577,420 disclose a ski boot constituted by an upper articulated on a shell base, the upper having two parts, namely, a rear part which is articulated on the shell base so as to swing back to permit introduction of the skier's foot into the boot, and a forward part or cuff, also articulated on the shell base and covering the latter particularly in the zone extending from the flexion fold to the instep, the enveloping shape of this lower forward portion of the cuff corresponding to the upper part of the shell base. This lower portion of the cuff comprises an elongated slot extending transversely on at least a portion of the circumference of the lower portion of the zone extending from the flexion fold to the instep.
In this groove may cursor a slide which acts as a movable abutment transmitting forces when the upper of the boot is flexed forwardly.